HP HP-67 - Page 193

Branching 189
To run the program to compute taxes on incomes of $15,000 and
$7,500:
Slide the W/PRGM-RUN switch werem Ji[[Irun to RUN.
Press Display
15000 B3 Dollars of tax.
7500 3 Dollars of tax.
Another place where you often want a program to make a decision is
within a loop. The loops that you have seen have to this point been
infinite loops—that is, once the calculator begins executing a loop,
it remains locked in that loop, executing the same set of instructions
over and over again, forever (or, more practically, until the calculator
overflows or you halt the running program by pressing or any
other key).
You can use the decision-making power of the conditional instructions
to shift program execution out of a loop. A conditional instruction
can shift execution out of a loop after a specified number of iterations
or when a certain value has been reached within the loop.
Example: As you know, your HP-67 contains a value for e, the base
of natural logarithms. (You can display the calculator’s value for e by
pressing 1 B} (€9).) The following program uses the series e = 1/0!
+ 11! + 1/2! + ... + 1/n!to approximate the value fore. After each
iteration through the loop, the latest approximation is displayed and
compared to the calculator’s value for e. When the two values are
equal, the execution is transferred out of the loop to stop the program.